作者iyenn (晓风)
看板Grad-ProbAsk
标题Re: [理工] [工数]-laplace
时间Wed Jul 29 16:08:21 2009
1.
let L(x(t))=X
2 5
SX-1 + 3X + --- X= ---
S S
S^2+3S+2 5
---------X = ---- +1
S S
5 S
X=----------- + ----------
(s+1)(s+2) (S+1)(S+2)
1 -1 -1 2
X=5{-----+ ------}+{ -----+ -----}
(s+1) (s+2) (S+1) (S+2)
x(t)=L^-1(X)
=5(e^-t - e^-2t)u(t) -e^-t + 2e^-2t
2. S
SY-1 + Y------- = e^-3s
S^2 + 4
S^3+4S+S
(----------)Y=e^-3s + 1
S^2+4
s^2 + 4 S^2+4
Y=----------e^-3s + --------
S(S^2 + 5) S(S^2+5)
4/5 (1/5)S 4/5 (1/5)S
={------- + ---------- ) e^-3s +{ ---- + ----------}
S S^2 + 5 S S^2 + 5
4 1 4 1
y={--- + --- cos{5^1/2 (t-3) }u(t-3)+ {--- + --- cos(5^1/2 t )
5 5 5 5
有错请不吝指教
--
电磁、电子、线代、工数
念书念得发了狂~欢迎讨论,共勉之
http://www.facebook.com/home.php#/iyen.li
--
※ 发信站: 批踢踢实业坊(ptt.cc)
◆ From: 123.193.214.165
1F：推 ooopppeeennn:3Q~ 07/29 16:30
2F：→ l1560ccdd:iy大大很厉害喔!! 也是应届考生吗 ?? 07/29 18:08